The present invention relates to a terminal device for an electric equipment that enables the terminal of a conductive material, such as a round terminal, to be connected easily without removing a terminal screw from a fixed terminal plate.
In general, in a terminal device for electric connection incorporated in an electric equipment, such as an electromagnetic contactor or switch, an end of a wiring is inserted between a fixed terminal plate with a tapped hole and a washer loosely supported by a male screw coupled to the fixed terminal plate, and the male screw is then tightened to connect the wiring to the electric equipment. When an electric wire having a round terminal with a round hole is connected to the terminal device, the male screw must be removed from the fixed terminal plate, and the male screw must be entered into the hole in the round terminal before the male screw is screwed into a tapped hole in the fixed terminal plate. This operation requires time to remove the male screw from the fixed terminal plate and involves mistakes, such as inadvertent dropping of the male screw, which requires more time to look for and pick up the dropped male screw, resulting in a degraded efficiency in the connecting operation. Thus, the terminal device for the electric equipment which improves efficiency in the connecting operation has been proposed.
FIG. 9 is a typical cross sectional view of a main part of a terminal device for an electric equipment with improved efficiency in the connecting operation, which is described in Japanese Patent Application Laid-Open(KOKAI) No. 60-130068. In this figure, a fixed terminal 13 fixed to a frame of the terminal device and formed of an insulating material includes a tapped hole 13a, and a male screw 12 to be coupled to the tapped hole 13a includes a washer 12a loosely and rotatably supported at a reduced diameter portion close to the head. A round hole 11h, into which a driver used to tighten or loosen the male screw 12 is inserted, is formed in a terminal cover 11 which covers the terminal device from above for preventing an electric shock. Furthermore, a flexible holding piece 11a engaging the bottom surface of the head of the male screw 12 to support the screw 12 is formed at the bottom of the round hole 11h. The terminal device is shipped with a gap maintained between the tip of the male screw 12 and the tapped hole 13a. At the time of connection, the round hole in the round terminal is fitted with the tip of the male screw 12 without loosening the screw as described above, and then the male screw 12 is pressed down and tightened.
FIG. 10 is a front view of a main part of a terminal device showing a different conventional example described in Japanese Patent Publication (KOKOKU) No. 4-4707, and FIGS. 11(a) and 11(b) are side views showing the shape of this terminal screw. In these figures, the terminal device comprises a fixed terminal 17 having a tapped hole 17a fixed to a frame 21 of an insulating member; and a terminal screw formed of a male screw 16 to be coupled to the tapped hole 17a and an inverse L-shaped washer 15 loosely and movably supported by the small diameter portion close to the head of the male screw.
The inverse L-shaped washer 15 has an inverse L shape and comprises a washer section penetrated by the male screw and a vertical portion with a bent portion 15a formed at the lower end of the vertical portion as shown in FIG. 11(b). The vertical portion is engaged with a guide groove 21a formed on the frame 21 side to vertically guide the male screw 16, thereby enabling the male screw 16 to be easily screwed into and removed from the tapped hole 17a in the fixed terminal 17. A plate spring 18 is installed at a bottom of the fixed terminal 17, and when the tip of the plate spring 18 is engaged with the bent portion 15a of the inverse L-shaped washer 15, the tip of the male screw 16 is separated from the tapped hole 17a and is held thereat. In this condition, a terminal 31 is placed around the tip of the male screw 16, and is then pressed down and tightened. In this manner, an electric wire can be connected without loosening the male screw 16.
In the terminal device in FIG. 9, when the male screw is tightened, the direction of the tip of the male screw is not stable in case the male screw is removed from the holding piece. This prevents the tip of the male screw from being easily screwed into the tapped hole 13a in the fixed terminal. In addition, if the electric wire is pulled when the male screw is inserted into the round hole in the round terminal, the male screw may slip from the holding piece. Furthermore, during the installation or removal of the wiring or during the additional connection of a round terminal, the terminal cover must be removed to thereby complicate the operation.
Although the terminal device in FIG. 10 reduces the number of the wiring steps and prevents a screw from being lost, it uses the plate spring to hold the inverse L-shaped washer in the upper part, resulting in an increased number of parts. In addition, the vertical portion of the inverse L-shaped washer can not be moved in a direction perpendicular to the direction of the sheet of the drawing due to the guide groove 21a of the frame 21. Therefore, when electric wires with different diameters are simultaneously connected on both sides of the male screw, normal tightening force does not allow the washer to be inclined, to thereby prevent a sufficient tightening force from being applied to the thinner electric wire. Furthermore, if a single wire is inserted on one side of the terminal screw and the screw is then tightened strongly, the connection between the washer section and vertical portion of the inverse L-shaped washer may be deformed to thereby make it impossible to reuse the device.
It is an object of the invention to provide a terminal device for an electric equipment that can reliably guide a male screw to a tapped hole in a fixed terminal without increasing the number of required parts and can certainly execute parallel connection of the electric wires with different diameters.